Python3.8 as a client

Hi;

Very interesting RESP implementation.
Could you please fix it and add ```set name [string tolower $name]``` as first line in ```proc lookup_command name```
It is needed because python 3.8 library redis send commands in upper case but lookup table names are in lowercase.
So invalid command name is occured.

After this small fix (name lowrecasing) all works correctly.

Thanks.